This invention relates to a fodder for fish being bred, especially a diet fodder for salmonoides, containing at least one agent for improving the visible pigmentation of the fillets. Likewise, the invention concerns a feeding procedure associated with this diet fodder.
Synthetic pigments are added to fodder for salmonoides in order to give the fillets a pink (salmon red) colour. The price for this additional fodder ingredient in the form of coloured matter constitutes approximately 20 percent of the total price of the diet fodder. The pigment content of the fodder should, thus, be reduced.
At the same time, the predictability for achieving a sufficiently visible fillet pigmentation is low in fish having been allotted a certain diet, and the fish breeders risk, therefore, to slaughter fish not having obtained the intentional pigmentation.
Therefore, it would be desirable to have at one""s disposal means to improve visible pigmentation in salmonoides and to put the means to use shortly before the slaughtering, without having to increase the pigment level when planning the composition of the diet.
Known pigmentation technique comprises to feed salmonoides with composite fodder substances containing between 30 and 100 mg/kg carotenoids, astaxanthin and/or canthaxanthin.
To meet target pigmentation at harvest, fish are sampled in the course of its growing period, and fillet pigmentation is monitored.
In order to secure an adequate pigmentation at the point of time for slaughtering, it may be necessary to use very high pigment levels. This increases the fodder costs and, thus, the production costs. Moreover, the reaction time is far too long. Many studies have shown that the pigment content of the fodder seems to have resulted in only 50% of the visual pigmentation which is measured by means of optical and visual means. Thus, increasing concentration of pigments does not secure an increasingly visible colouring of the fillets. Known pigmenting technique associated with desired fillet colour of slaughtered fish thusly bred, especially salmonoides, is, therefore, not predictable to a desired extent.
An advantage of this invention is to provide a diet for feeding fish especially salmonoides during a short period of time prior to slaughtering, in order to increase the visible pigmentation of the fish meat.
This advantage is realized by means of a fodder containing a concentration of at least 8.6% lysine based on the protein in a diet fodder, and through a relatively brief feeding period, with such diet fodderxe2x80x944-8 weeks before slaughtering.
The lysine-containing diet fodder according to the invention, as utilized during the indicated short feeding period, achieves a statistically significant increase in the pigmentation of the fillets as perceived visually, without having to alter the pigment levels in the diet fodder.